This document relates to power amplifier systems and components therein based on metamaterial structures.
The propagation of electromagnetic waves in most materials obeys the right-hand rule for the (E,H,β) vector fields, considering the electrical field E, the magnetic field H, and the wave vector β (or propagation constant). The phase velocity direction is the same as the direction of the signal energy propagation (group velocity) and the refractive index is a positive number. Such materials are referred to as Right Handed (RH) materials. Most natural materials are RH materials. Artificial materials can also be RH materials.
A metamaterial (MTM) has an artificial structure. When designed with a structural average unit cell size much smaller than the wavelength of the electromagnetic energy guided by the metamaterial, the metamaterial can behave like a homogeneous medium to the guided electromagnetic energy. Unlike RH materials, a metamaterial can exhibit a negative refractive index, and the phase velocity direction is opposite to the direction of the signal energy propagation, wherein the relative directions of the (E,H,β) vector fields follow the left-hand rule. Metamaterials which have a negative index of refraction with simultaneous negative permittivity ∈ and permeability μ are referred to as pure Left Handed (LH) metamaterials.
Many metamaterials are mixtures of LH metamaterials and RH materials and thus are Composite Right and Left Handed (CRLH) metamaterials. A CRLH metamaterial can behave like an LH metamaterial at low frequencies and an RH material at high frequencies. Implementations and properties of various CRLH metamaterials are described in, for example, Caloz and Itoh, “Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications,” John Wiley & Sons (2006). CRLH metamaterials and their applications in antennas are described by Tatsuo Itoh in “Invited paper: Prospects for Metamaterials,” Electronics Letters, Vol. 40, No. 16 (August, 2004).
CRLH metamaterials may be structured and engineered to exhibit electromagnetic properties tailored to specific applications and may be used in applications where it may be difficult, impractical or infeasible to use other materials. In addition, CRLH metamaterials may be used to develop new applications and to construct new devices that may not be possible with RH materials.
In some applications, MTM and CRLH structures and components are based on a technology which applies the concept of Left-handed (LH) structures. As used herein, the terms “metamaterial,” “MTM,” “CRLH,” and “CRLH MTM” refer to composite LH and RH structures engineered using conventional dielectric and conductive materials to produce unique electromagnetic properties, wherein such a composite unit cell is much smaller than the wavelength of the propagating electromagnetic waves.
Metamaterial technology, as used herein, includes technical means, methods, devices, inventions and engineering works which allow compact devices composed of conductive and dielectric parts and are used to receive and transmit electromagnetic waves. Using MTM technology, antennas and RF components may be made very compactly in comparison to competing methods and may be very closely spaced to each other or to other nearby components while at the same time minimizing undesirable interference and electromagnetic coupling. Such antennas and RF components further exhibit useful and unique electromagnetic behavior that results from one or more of a variety of structures to design, integrate, and optimize antennas and RF components inside wireless communications devices.
CRLH structures are structures that behave as structures exhibiting simultaneous negative permittivity (∈) and negative permeability (μ) in a frequency range and simultaneous positive ∈ and positive μ in another frequency range. Transmission-line (TL) based CRLH structures are structures that enable TL propagation and behave as structures exhibiting simultaneous negative permittivity (∈) and negative permeability (μ) in a frequency range and simultaneous positive ∈ and positive μ in another frequency range. The CRLH based antennas and TLs may be designed and implemented with and without conventional RF design structures.
Antennas, RF components and other devices made of conventional conductive and dielectric parts may be referred to as “MTM antennas,” “MTM components,” and so forth, when they are designed to behave as an MTM structure. MTM components may be easily fabricated using conventional conductive and insulating materials and standard manufacturing technologies including but not limited to: printing, etching, and subtracting conductive layers on substrates such as FR4, ceramics, LTCC, MMIC, flexible films, plastic or even paper.